Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Matrix problem help. solve the remaining equation and find the value(s) for x

  1. Oct 26, 2011 #1
    1. The problem statement, all variables and given/known data
    | x 0 c|
    | -1 x b| = 0
    | 0 -1 a|
    2. Relevant equations

    3. The attempt at a solution
    As best as I can tell I would end up with x * (xa - (-1b)) and -1c and then I would end up with Ax^2 + BX + C which leaves me confused am I looking at a quadratic equation for the answer or is there a way to get numerical values out of it?
  2. jcsd
  3. Oct 26, 2011 #2


    Staff: Mentor

    Your problem statement says that the determinant of your matrix is zero.

    What equation represents this?
  4. Oct 26, 2011 #3


    User Avatar
    Homework Helper

    I presume you are taking the determinant and setting it equal to zero. If so, what you've done looks right. Remember the solution to a quadratic equation? Also, you can only get a numerical answer if you know the values of a,b,c. Otherwise, the answer will be an expression involving a,b,c.
  5. Oct 27, 2011 #4

    I am using det(a)=A11(A22*A33-A23*A32)-A12(A21*A33-A23*A31)+A13(A21*A32-A22*A31)

    Yes it is equal to zero sorry, new here.

    Ax^2+bx+c=0 so I am assuming my answer would be x = [-b ± √(b^2 - 4ac) ]/2a
  6. Oct 27, 2011 #5


    Staff: Mentor

    Yes, that's right.
  7. Oct 28, 2011 #6
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook